Currently, GetVSPath() is called twice. The result if that call is used
locally in both situations.

This commit makes only one call, passing the result to where it is
needed.

Change-Id: I186bd7f0387091ad16c2791de99d1de8a89f266c
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/tools/depot_tools/+/3510528
Auto-Submit: Chris Blume <cblume@chromium.org>
Reviewed-by: Bruce Dawson <brucedawson@chromium.org>
Commit-Queue: Bruce Dawson <brucedawson@chromium.org>